Lesson 5 Flashcards
What is nondisjunction?
Nondisjunction occurs when homologous chromosomes (in meiosis I) or chromatid pairs (in meiosis II) fail to separate properly during anaphase, leading to gametes with an abnormal number of chromosomes.
How does nondisjunction occur in meiosis I?
In meiosis I, homologous chromosomes fail to separate, resulting in gametes with an extra chromosome (n + 1) or a missing chromosome (n - 1).
What happens during nondisjunction in meiosis II?
In meiosis II, chromatid pairs fail to separate during anaphase II, leading to gametes with either an extra chromatid or a missing one.
What does ‘n + 1’ mean in the context of nondisjunction?
‘n + 1’ means that there is an extra chromosome, resulting in a gamete with one more chromosome than normal (e.g., 23 + 1 = 24 chromosomes).
What does ‘n - 1’ mean in the context of nondisjunction?
‘n - 1’ means that there is a missing chromosome, resulting in a gamete with one fewer chromosome than normal (e.g., 23 - 1 = 22 chromosomes).
What is a genetic disorder?
A genetic disorder is a disease caused by an undesirable change in the DNA of an individual, often leading to abnormal growth, development, or function.
What is trisomy?
Trisomy is a chromosomal abnormality where an individual has three homologous chromosomes instead of two (e.g., Trisomy 21 or Down syndrome).
What is monosomy?
Monosomy is a chromosomal abnormality where an individual has only one chromosome from a homologous pair instead of two (e.g., Monosomy 23 or Turner syndrome).
What is Down syndrome?
Down syndrome is a chromosomal abnormality where an individual has three copies of chromosome 21 (Trisomy 21), leading to developmental delays and intellectual disabilities.
What is Turner syndrome?
Turner syndrome is a chromosomal abnormality where an individual has only one X chromosome and no second sex chromosome, causing short stature, underdeveloped sexual characteristics, and infertility.
What is a karyotype?
A karyotype is an organized display of an organism’s chromosomes, allowing for the visualization of both autosomes and sex chromosomes to identify chromosomal abnormalities.
How are karyotypes used to diagnose disorders?
Karyotypes are used to detect chromosomal abnormalities, determine an individual’s sex, and diagnose disorders like Down syndrome (Trisomy 21) or Turner syndrome (Monosomy 23).
What would a karyotype showing 47 chromosomes, including an extra chromosome 21, indicate?
It would indicate Down syndrome (Trisomy 21), where the individual has three copies of chromosome 21.
What would a karyotype showing 45 chromosomes, with only one X chromosome, indicate?
It would indicate Turner syndrome (Monosomy 23), where the individual has only one X chromosome and no second sex chromosome.
What is the sex of an individual with a karyotype showing 47 chromosomes, one X, and one Y chromosome?
The sex would be Male, with a chromosomal abnormality like Klinefelter syndrome.
Could this be the karyotype of a human sperm cell: 22 chromosomes with both X and Y chromosomes?
No. A human sperm cell should carry either an X or a Y chromosome, but not both. This would indicate an abnormality.
Why are there more types of trisomy disorders than monosomy disorders?
It is less harmful to gain one extra chromosome (trisomy) than to lose one (monosomy), as losing a chromosome often leads to miscarriage, while trisomy can still allow survival but may result in disorders.
